It depends on the age. Even as young kids, boys have some advantages, as the study linked above showed. But by the end of high school the kids have been through puberty, and a significant number of under 18 boys are able to beat world records set by adult women, putting them far ahead of their female peers.
I tend to agree that it depends what age the child began transition. Male puberty confers a huge laundry list of athletic benefits, which studies show are not undone by a few years of hormone therapy.
Some advantages such as greater height, broader shoulders, narrower pelvis, stronger bones, etc can never be removed.
The reason trans men and boys are largely ignored in this discussion is that no one believes they have an advantage over cis men. Quite the reverse. If they are not taking testosterone there is no real reason they should be barred from women’s and girl’s competitions, and if they are then they can be allowed to compete in men’s without unfairly disadvantaging anyone but themselves.
As for the argument that everyone should compete according to gender identity with no requirements for hormones etc, completely ignoring the physiological differences between the sexes, this is a logically inconsistent position. Those physiological differences between (cis) men and women are the only justification for allowing separate mens and women’s events in sport, something that would otherwise be considered just as discriminatory as having separate events for different races or religions. Especially given the massive disparity in rewards that exists in many sports. If sportswomen were able to compete against men they would long since have campaigned to be allowed to do so.